The invention concerns an installation for producing multi-layer composite tubes, comprising a shaping device for shaping a metal strip into a metal tube with overlapping longitudinal edges, a welding device for welding the overlapping longitudinal edges, an extruder station with an extrusion head which adjoins the shaping device and which is connected to a first extruder for applying an inner plastic layer and a second extruder for applying an outer plastic layer to the metal tube, and a cooling device for cooling the multi-layer composite tube, which are arranged in succession in a production line.
Installations of that kind are known per se. In those known installations, the extrusion head is fixedly connected to the first extruder for the inner plastic layer. The second extruder which is provided for the outer plastic layer is spatially separated from the unit consisting of the extrusion head and the first extruder and is suitably connected in flow relationship to the extrusion head. That structure adversely affects both the accuracy of assembly and also the production speed for producing the multi-layer composite tubes. A further deficiency of those known installations is that a change in the composite tube nominal size, that is to say converting the installation from one composite tube diameter to a desired different composite tube diameter, is possible only at the cost of a considerable amount of time and assembly complication.
In consideration of those factors the object of the present invention is to provide an installation of the kind set forth in the opening part of this specification, which, with a comparatively high production speed, permits optimum composite tube quality, while a change in composite tube nominal size is also possible relatively easily and without taking up a great deal of time.
In accordance with the invention, in an installation of the kind set forth in the opening part of this specification, that object is attained in that the extrusion head of the extruder station is disposed stationarily and that the first and the second extruders are arranged facing towards each other in mutual alignment in a line laterally beside the extrusion head in parallel relationship with the production line, wherein the extrusion head in the production line is provided between the first and the second extruders.
In this respect the term xe2x80x98production linexe2x80x99 means the line along which the metal strip moves along the shaping device for shaping the metal strip to form the respective metal tube, to the welding device for welding the overlapping longitudinal edges of the shaped metal strip to form the metal tube, wherein the production line is defined in particular also by the extruder station, that is to say by the extrusion head, and thereafter by the cooling device for cooling the produced multi-layer composite tube. The metal strip or the multi-layer composite tube produced with the installation is moved in a straight line at a given, comparatively high advance speed through the installation. While, in known installations of the kind set forth in the opening part of this specification, with a given composite tube diameter, that is to say nominal size, the advance speed is of the order of magnitude for example of 15 m/min, it is possible with the installation according to the invention and for the same composite tube diameter for the production speed to be increased to the order of magnitude of 25 m/min, that is to say by 67%, in which case that advantage of the installation according to the invention involves the advantages of the possibility of a simple and time-saving change in composite tube diameter with the installation according to the invention being of an arrangement which saves on floor area or space. In particular the fact that, in the installation according to the invention, the extrusion head of the extruder station is stationarily provided alone, that is to say without the first extruder for the inner plastic layer, and the fact that the first and second extruders are provided in alignment with each other in a line in mutually facing relationship laterally beside the extrusion head means that the installation is of a design configuration which saves on floor area, with the advantage that temperature-related changes in length of the two extruders are compensated. That has a positive effect on the accuracy of the installation construction and the accuracy of manufacture of the multi-layer composite tubes produced with the installation according to the invention.
It has proven to be advantageous if, in the installation according to the invention, there are third and fourth extruders for bonding agents, wherein the third extruder is associated with the first extruder for the inner plastic layer and the fourth extruder is associated with the second extruder for the outer plastic layer of the multi-layer composite tube. It will be appreciated that it would also be possible, in an installation according to the invention, for the extruder station to be combined with a single extruder for a bonding agent. That third extruder would then be combined with a switching device for combining the bonding agent both with the first extruder and with the second extruder in order to apply the inner plastic layer and the outer plastic layer in firmly adhering relationship to the metal tube by means of the bonding agent.
The third and the fourth extruders for bonding agent are desirably cardanically mounted to associated stationary column devices. Such a structure correspondingly improves the accuracy of the installation and the productivity thereof because the adjustability thereof is optimised.
In the installation according to the invention it has proven to be advantageous if the welding device has a welding station with an ultrasound welding wheel, wherein the welding station is displaceable in respect of height in relation to the extrusion head in a first direction in space parallel to the production line, in a second direction in space perpendicular thereto transversely with respect to the production line and in a third direction in space perpendicular to the first and second directions in space, and is pivotable about a pivot axis oriented in the first direction in space. That displacement and/or pivotal movement can be implemented pneumatically or mechanically, for example by spindle drives. That displaceability permits not only a time-saving change in nominal size, that is to say the time-saving possibility of converting the installation from one composite tube diameter to a desired different composite tube diameter, but it also affords the considerable advantage that access to the installation is better possible in the case of such changes in nominal size or disturbances in production. Possible disturbances in production can be very rapidly dealt with.
In the installation according to the invention, the ultrasound welding wheel is desirably connected to a drive motor for controlled rotary drive of the welding wheel. By means of the drive motor, the speed of rotation of the ultrasound welding wheel which forms a sonotrode is accurately matched to the advance speed of the installation, that is to say the advance speed of the metal strip which is shaped to form the metal tube, in order to produce a highly accurate metal tube which is provided with the inner and outer plastic layers in firmly adhering relationship.
To produce the highly precise metal tube from the corresponding metal strip, it has proven to be desirable if adjacent to the welding device are two closing roller devices which each have more than two closing rollers which are distributed at the periphery and which adjoin each other. Each of the two closing roller devices may have four mutually adjoining closing rollers.
In order to permit adaptation to different material qualities of metal strips which are to be shaped to form the metal tube, in respect of dimensional tolerances, stiffnesses of the material and so forth, it is desirable if at least some of the closing rollers of the respective closing roller device are radially displaceable.
In accordance with the invention, a precise change in composite tube nominal size is permitted in a still further better fashion if, in the installation according to the invention, the shaping device has a base element on which pairs of shaping rollers are arranged in succession at a spacing from each other in the advance direction of the metal strip to be shaped, wherein the base element is displaceable in the second direction in space transversely with respect to the production line and in the third direction in space vertically and is pivotable about a pivot axis oriented in the second direction in space and about a pivot axis oriented in the third direction in space. Such a linear and virtually cardamic arrangement of the base element means that the pairs of shaping rollers provided thereon are precisely adjustable in such a fashion as to save time, which has an advantageous effect on the level of productivity of the installation according to the invention. In addition, by virtue of this design configuration of the last-mentioned kind, it is also easily possible for the shaping device to be very quickly and accurately converted and set to the respective metal strip width and thus to the desired tube diameter. In this case adjusting wheels can be provided for displacement in the second direction in space and about the pivot axis oriented in the second direction in space, and for displacement in the third direction in space and about the pivot axis oriented in the third direction in space. The adjusting wheels may be for example hand wheels in order to implement suitable manual adjustment.
In the installation according to the invention arranged upstream of the shaping device in the production direction is a metal strip unwinding device which is displaceable in the second direction in space transversely with respect to the production line.
That transverse displaceability of the metal strip unwinding device means that it is advantageously easily possible for the metal strip unwinding device to be accurately set in dependence on the width of the respective metal strip to be processed, that is to say the metal strip unwinding device and thus the respective metal strip can be centered accurately, that is to say exactly, in relation to the production line. That centering displacement of the metal strip unwinding device is possible in a simple fashion and in such a way as to save a great deal of time.
The metal strip unwinding device may have a single reel mounting for a metal strip reel, but it is preferred if the metal strip unwinding device has a support element with two reel mountings, wherein the support element is rotatable about a vertical axis and the two reel mountings are provided at mutually remote sides of the support element. In comparison with a metal strip unwinding device having a single reel mounting, such a design configuration of the last-mentioned kind enjoys the advantage that it is possible to change from an exhausted metal strip reel to an unused fresh metal strip reel in such a way as to save time. That also has an advantageous effect on the level of productivity of the installation according to the invention.
Particularly if, in the installation according to the invention, the metal strip unwinding device has a support element with a single reel mounting, it is desirable If provided between the metal strip unwinding device and the metal strip shaping device is a metal strip storage device which has vertical side walls arranged parallel to each other and to the production line, because it is possible for a suitable end portion or a residual length of the exhausted metal strip reel to be deposited in that metal strip storage device and for the end of that exhausted metal strip to be fixedly connected to the beginning of a fresh metal strip reel. During that operation of joining the two ends, which is desirably effected by ultrasonic welding, the residue of the metal strip, which is in the metal strip storage device, can be continuously subjected to further processing to form the multi-layer composite tube. In that respect, the vertical side walls of the metal strip storage device which are arranged parallel to each other and to the production line provide a guidance effect for the stored length of metal strip.
From the point of view of being able to process metal strips of different strip widths with a high level of productivity on the Installation according to the invention, it is desirable if the side walls of the metal strip storage device are simultaneously displaceable symmetrically in mirror-image relationship with respect to the production line. That displacement can be effected for example by means of a hand wheel which is suitably combined with the two side walls of the metal strip storage device. That can be effected for example by spindle drives and a belt or the like which drives the spindles in common relationship.
In order to provide for cooling of the corresponding initial portion of the multi-layer composite tube even during each start-up phase of operation of the installation according to the invention, that is to say during the operation of filling the cooling device with the cooling liquid, it is desirable if, in the installation according to the invention, the cooling device has an elongate liquid bath with a nozzle device and with composite tube hold-down devices, wherein the nozzle device is formed with mutually spaced nozzle openings which are directed towards the production line. The nozzle openings which are oriented towards the production line, that is to say the multi-layer composite tube, provide that the cooling liquid is already directed during the operation of filling the liquid bath towards the leading-end or initial portion of the multi-layer composite tube in order to produce a suitable cooling effect. The multi-layer composite tube is positioned in a defined fashion in the elongate liquid bath of the cooling device by means of the composite tube hold-down devices, that is to say the multi-layer composite tube is prevented from floating up in the liquid bath. Such a floating effect would be caused by the buoyancy action of the multi-layer composite tube, without the use of the composite tube hold-down devices. That buoyancy action results from the fact that there is a corresponding increased pressure in the interior of the multi-layer composite tube. That increased pressure is necessary in order to precisely form the metal tube with the inner plastic layer firmly adhering thereto.
The respective composite tube hold-down device can have two mutually spaced rollers which are mounted on a pivotal lever. Such a per se known design configuration affords the advantage that metal-layer composite tubes of different nominal diameters can be readily precisely correctly positioned in the elongate liquid bath of the cooling device.
The above-mentioned increased pressure in the interior of the multi-layer composite tube can be produced in per se known manner by a mandrel or bar, as is described for example in EP 0 581 208 B1. In the case of the installation according to the invention, it has been found to be desirable to provide in the liquid bath a tube clamping-off device with squeeze-off jaws, which device can be reciprocated along the liquid bath, and to provide at the beginning of the liquid bath a first actuating device for closing the squeeze-off jaws and for keeping them closed and at the end of the elongate liquid bath a second actuating device for opening the squeeze-off jaws and for keeping them open. The multi-layer composite tube produced in the installation is squeezed off at a given location by means of the squeeze-off jaws of the tube clamping-off device, with the interior of the tube being closed by the inner plastic layer which is still in a plastic condition at that location. That makes It possible to produce a suitable increased pressure in the interior of the tube. In the installation according to the invention, the tube clamping-off device with the squeeze-off jaws can be reciprocated in the elongate liquid bath by electric motor means. The forward movement between the first and second actuating devices is effected in that respect at a speed adapted to the advance speed of the multi-layer composite tube produced in the installation. The return movement from the second actuating device to the first actuating device can also be effected at a higher speed.
In the installation according to the invention, it is desirable if disposed downstream of the cooling device in the production direction is an optical tube monitoring device, a printer, a tube draw-off device and a tube winding-up device. The optical outer tube monitoring device can have a number of video cameras. The video cameras are connected together and combined with a control device of the installation according to the invention in such a way that the installation is immediately stopped if the video cameras detect production defects on the produced multi-layer composite tube.
The installation according to the invention can be precisely set up in a relatively simple fashion without entailing a great deal of time, if there is provided a two-part base device having a first and a second base portion, wherein arranged on the first base portion are the metal strip unwinding device, the metal strip storage device and the extruder station, and arranged on the second base portion are the optical tube monitoring device, the printer, the tube draw-off device and the tube winding-up device, wherein the first and second base portions are connected together by means of the cooling device. The first and second base portions can be in the form of base plates with suitable cavities or shaftsxe2x80x94virtually like palettesxe2x80x94in order also to serve to receive the installation materials of the installation according to the invention.